#16 Property Binding | Angular Components & Directives | A Complete Angular Course
Summary
TLDRThis lecture delves into the concept of property binding in web development, contrasting it with string interpolation for one-way data binding. It illustrates how property binding is used to assign dynamic values to HTML attributes, as opposed to static data display with string interpolation. Examples provided include binding an image source, enabling/disabling a button based on stock status, and dynamically setting input values. The tutorial also clarifies the difference between HTML attributes and properties, and introduces attribute binding for accessibility and data attributes.
Takeaways
- 📝 String interpolation and property binding are both used for one-way data binding in Angular, passing data from the component class to the view template.
- 🖼 String interpolation is used for displaying data in HTML, such as product titles or names.
- 🔗 Property binding is used to bind a DOM object's property to a value in the component class, allowing dynamic manipulation of the DOM.
- 📸 An example of property binding is setting the 'src' attribute of an image tag to a product's image path stored in the component class.
- 🔄 Property binding can dynamically assign values to HTML attributes, such as enabling or disabling a button based on product stock.
- 🚫 String interpolation cannot be used for certain HTML attributes like 'disabled', 'hidden', and 'checked', where property binding is necessary.
- 🔑 The difference between HTML attributes and properties is that attributes represent initial values and do not change, while properties represent current values and can be dynamic.
- 🛑 For HTML attributes that do not have corresponding properties, such as 'aria-hidden', attribute binding must be used instead of property binding.
- 🔄 An alternative syntax for property binding is using 'bind' followed by the attribute name, like 'bind-value' for input elements.
- 🔧 Property binding is essential for creating interactive and dynamic web applications, allowing for real-time updates to the UI based on data changes.
- 🤔 Understanding the distinction between string interpolation and property binding is crucial for developers to make the right choice in different scenarios in Angular applications.
Q & A
What is the purpose of string interpolation and property binding in Angular?
-String interpolation and property binding in Angular are used for one-way data binding, allowing data to be passed from the component class to the view template. String interpolation is typically used for displaying data in HTML, while property binding is used to bind a property of a DOM object to a value in the component class, enabling dynamic manipulation of the DOM.
How does string interpolation differ from property binding in Angular?
-String interpolation is used for displaying static or dynamic text within an HTML template, whereas property binding is used to bind a dynamic value to an HTML attribute, allowing for more complex interactions with the DOM elements.
What is an example of when to use string interpolation in Angular?
-String interpolation can be used to display the title or name of a product within an HTML template, as it is suitable for showing a piece of data without the need for any further DOM manipulation.
Can property binding be used to manipulate the DOM elements in Angular?
-Yes, property binding allows for the manipulation of DOM elements by binding their properties to dynamic values from the component class, enabling actions such as showing or hiding elements, enabling or disabling buttons, and more.
How can you bind an image source to a product object in Angular?
-You can create a property within the product object, such as 'pImage', and assign the image path to this property. Then, in the view template, use property binding syntax to bind the 'src' attribute of the 'img' tag to the 'pImage' property of the product object.
What is the syntax for property binding in Angular?
-The syntax for property binding in Angular involves wrapping the HTML attribute you want to bind within square brackets and assigning a TypeScript expression within double quotes.
Why can't string interpolation be used for all HTML attributes?
-String interpolation cannot be used for certain HTML attributes like 'disabled', 'hidden', and 'checked' because they require a boolean value to enable or disable their functionality, which is not suitable for the text-based output of string interpolation.
What is the alternative syntax to using square brackets for property binding in Angular?
-The alternative syntax for property binding in Angular is to use the 'bind' prefix followed by the attribute name, such as 'bindValue' for the 'value' attribute of an input element.
How can you make a button disabled based on the stock status of a product in Angular?
-You can use property binding to bind the 'disabled' attribute of the button to a TypeScript expression that checks the 'inStock' property of the product. If 'inStock' is less than or equal to 0, the button will be disabled; otherwise, it will be enabled.
What is the difference between HTML attributes and HTML properties?
-HTML attributes represent the initial values set in the markup and are static, while HTML properties represent the current values that can change dynamically as the page loads and scripts execute.
Can you provide an example of using attribute binding in Angular?
-Attribute binding can be used for accessibility attributes like 'aria-hidden'. Instead of using square brackets, you would use 'attr.' followed by the attribute name, and assign a TypeScript expression to it within double quotes.
Outlines
🔗 Introduction to Property Binding
This paragraph introduces the concept of property binding in web development, contrasting it with string interpolation. While string interpolation is used for displaying static data, property binding is employed for one-way data binding to pass dynamic data from a component class to the view template. The lecturer uses an example of displaying a product image to illustrate property binding, explaining the process of assigning a dynamic image path to an HTML image element's 'src' attribute using Angular's property binding syntax.
🛍️ Manipulating UI with Property Binding
The second paragraph delves into using property binding to manipulate user interface elements dynamically. It discusses enabling and disabling a 'Buy Now' button based on the product's stock status, demonstrating how to use property binding to assign a boolean value to the 'disabled' attribute of a button. The lecturer also clarifies the difference between using string interpolation and property binding, especially for HTML attributes that require dynamic values, such as 'disabled', 'hidden', and 'checked'.
📝 Advanced Property Binding Techniques
The final paragraph explores advanced property binding techniques, including the use of the 'bind' prefix as an alternative to square brackets for binding properties. It also distinguishes between HTML attributes and properties, explaining that attributes are initial values that do not change, while properties represent current values that can change. The lecturer provides an example of binding an 'aria-hidden' attribute using attribute binding syntax due to its nature as an accessibility attribute. The paragraph concludes with an invitation for questions and well-wishes for the audience.
Mindmap
Keywords
💡String Interpolation
💡Property Binding
💡One-way Data Binding
💡Component Class
💡View Template
💡HTML Attributes
💡DOM Manipulation
💡TypeScript Expression
💡Attribute Binding
💡Data Binding
Highlights
Introduction to string interpolation and property binding for one-way data binding in Angular.
Explanation of the difference between string interpolation and property binding, with examples.
Demonstration of using string interpolation for displaying data in HTML.
Introduction to property binding for binding a DOM object's property to a value in the component class.
Example of using property binding to display a product image by binding the 'src' attribute of an 'img' tag.
Explanation of hardcoding the source path versus using a property in the component class.
Step-by-step guide on adding an image to a product list using Angular's property binding.
Use of property binding syntax for dynamic values in HTML attributes.
Example of enabling and disabling a 'Buy Now' button based on product stock using property binding.
Clarification on when to use property binding over string interpolation for certain HTML attributes like 'disabled'.
Illustration of incorrect use of string interpolation for attributes that require property binding.
Introduction to the concept of attribute binding in Angular.
Explanation of the difference between HTML attributes and properties, and when to use attribute binding.
Demonstration of attribute binding using 'attr.' syntax for accessibility and data attributes.
Alternative method of using 'bind' keyword for property binding instead of square brackets.
Final summary of property binding and attribute binding in Angular for one-way data binding.
Transcripts
in the last lecture we learned about
string interpolation we use string
interpolation to achieve one-way data
binding by passing data from the
component class to its view template now
in this lecture we are going to talk
about property binding we also use
property binding to achieve one-way data
binding by passing data from the
component class to its view template but
the difference between string
interpolation and property binding is
that
in string interpolation we use it for
displaying a piece of data in the HTML
for example displaying the title of a
product or name of the product or
something like that
but we use property binding to bind the
property of a dome object to some value
which we have in the component class
in this way property binding allows us
to show our high Dom element or
manipulate the Dom in some other way
so in this lecture let's go ahead and
let's learn more about property binding
with some examples
again here we have our product list
component.html file and here we have
product list component class
now what we want is here we want to show
an image for this product
so before this paragraph element I'll go
ahead and I'll use image tag
and in there let's go ahead and let's
specify the source tag and to this
Source tag we need to specify the path
of a image file
now in order to save some time here in
the sample files folder I have one image
let me drag it and let's go to vs code
and let me go ahead and let me paste it
inside this assets folder and inside we
have that image folder so let me put it
inside this image folder
okay and we don't need this planet.jpg
file anymore so let me go ahead and let
me delete it
okay and I want to display this product
image
before the product details so for that
we can say it is in assets folder in
there we have the images folder and in
there we have iPhone dot PNG okay so let
me save the changes
and if we go to the web page that image
should be displayed
okay now here what we are doing is we
are hard coding this Source path so we
are hard coding this Source path and
we're assigning to this Source attribute
now instead of doing it like this what
we can do is in our component class we
can create a property or maybe inside
this product object itself we can create
a property let's say p image okay and to
that we can assign that value
so let me go ahead and let me grab that
image path from here I'll cut it
and I'll paste it here and now we want
to use this property of this product
object in our view template
so here either we can use string
interpolation syntax like this and there
we can say product Dot
P image
and if you save the changes if you go
back to the web page
that image is still displayed
so we can also use string interpolation
syntax here but instead of using string
interpolation syntax since here we are
trying to assign some Dynamic value to
an attribute of an HTML element we can
use property binding syntax
so here we will not use string
interpolation syntax instead we will use
property binding syntax and for the
property binding all we have to do is we
have to wrap this attribute within
square brackets like this and then we
can assign a set of double quotes and
inside these double quotes we can write
any typescript expression okay so inside
these double quotes we can write any
typescript expression
here we want to use the P image property
of the product object so we can say
product
dot the image
and that should be it if I save the
changes and if you go back to the web
page that image should still be
displayed there but now we are using
property binding syntax
so here we are binding the property of a
Dom element to a dynamic value a value
from our component class
right
so this is what property binding is
now let's take one more example so after
these product details let's go ahead and
let's add a button element
and there let's say by now
okay and on this button element let's go
ahead and let's add a property called
disabled
and what we want is we want to make this
buy now button disabled If the product
is not in stock
but if the product is in stock in that
case we don't want to make this button
disabled So currently since we have used
this disabled property if you go back to
the web page there you will see we have
this buy now button but it is disabled
okay so what we want is If the product
is in stock we don't want to disable
this button this button should not be
disabled but if the product is not in
stock in that case this buy now button
should be disabled so let's go ahead and
let's do that for that let's go back to
vs code and again here I'm going to use
property binding syntax and for property
binding we wrap the property the HTML
attribute within square brackets and to
that we can assign double quotes and in
there we can write any typescript
expression
now here we are simply going to check if
product in stock is not greater than 0
so I'll paste it here and we'll simply
use a not operator
on this expression so I'll wrap it
within parenthesis like this and I'll
use a not operator
So currently if you go to this product
list component.ts there you will see
that in stock is 0 so if you go to the
web page
at this time the button should be
disabled but if we go back and if we
change this in stock to maybe 10 and if
we save the changes and now if we go
back you will see that that button is
enabled
so you see here we are passing data from
the component class to its view template
and there we are assigning that data to
an HTML property now you might say here
if we can also use string interpolation
then why do we need another feature like
property binding
well that's because we cannot use string
interpolation for all types of HTML
attribute for example in case of this
disabled if I use string interpolation
instead of property binding so if I wrap
this Within
double set of curly braces like this
here it will not work if I save the
changes and if I go to the web page
there you see the button is disabled and
it is not working properly
so for HTML attributes like
disabled hidden and checked
for these three HTML attributes the
string interpolation syntax will not
work in that case you will have to use
property binding syntax
and that's why we have string
interpolation as well as property
binding for one-way data binding when we
want to display some data in the HTML we
use string interpolation but when we
want to assign some Dynamic value to an
HTML attribute there we use property
binding
okay I hope it is clear
so here instead of using string
interpolation syntax let's use property
binding
okay and let's wrap this property this
HTML attribute within square brackets
and now if we go back it should be
working
see button is enabled but if we change
it to 0
if we go back to the web page
now it is disabled
all right
so I hope with these two examples now
you know what is property binding and
how we can use it as I mentioned when we
wrap an HTML attribute within square
brackets and to that when we assign
double quotes inside that double quotes
we can write any typescript expression
let me show you one more example of
property binding so let's go ahead and
let's create an input element
in this input element let's say I want
to have a value property and in this
value I want to show some value but I
want to show that value dynamically
so basically what I want is in the
component I want to have a property
here let me go ahead and let me create a
property and I will call this property
maybe name and let's say John Doe okay
so here we have a name property assigned
with this value John Doe and now we want
to display this value inside the input
element
so here to this value we want to assign
the values stored in this name property
for that again we can use property
binding syntax so what we will do is
we'll wrap this value within square
brackets and then here we can write any
typescript expression here we simply
want to use this name property so I'll
go ahead and I will assign that name
property to this value attribute if I
save the changes if you go back to the
web page now we should also have an
input element and there you will see
that the value is John Doe the value is
stored in this name property
now there is one more thing which you
will not find in many tutorials and that
is instead of using these square
brackets like this what we can also do
is we can use bind before these
attributes for example I can say
bind value and in this way also it
should be working if I save the changes
and if we go back you see still this
input element is assigned with the value
of the name property but now for the
property binding we are not using square
brackets we are using bind
same thing we can do here so instead of
wrapping this disabled attribute within
square brackets I can use
bind
like this and if you go to the web page
button is disabled
let's go back to component cluster let's
change in stock to 10
let's save the changes let's go back to
the web page and now the button is
enabled so you can also use
bind instead of square brackets but
using square brackets is more common so
we will use that itself
and here also instead of bind we will
use square brackets
now just like property binding we also
have something called as attribute
binding
now here you can ask what is the
difference between an HTML attribute and
an HTML property the HTML attribute
represents the initial value and it does
not change but a property represents the
current value and it can change for
example we have accessibility attributes
like area level area head and area
expanded area control or we have data
attributes like data ID data name data
value and we also have this call span
which is a table attribute we use it on
table columns so these attributes when
you try to bind them using property
binding you will get an error there you
need to bind them using attribute
binding so let's try to understand what
is that
so on this input element itself let's go
ahead and let's try to use an
accessibility attribute called
area hidden
okay and here let's try to bind it by
wrapping it within square brackets like
this and you see here we are getting an
error and the error says can't bind to
area head and since it is not a known
property okay that means this area
hidden here it is not a property it is
an attribute and for binding attributes
all we have to do is we have to say attr
dot and then the attribute name and then
again Within These double quotes we can
assign any typescript expression to
these attributes
so if you want to perform attribute
binding you can do it something like
this
all right so this is all from this
lecture if you have any questions then
feel free to ask it thank you for
listening and have a great day
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